GuideIntermediate

Architecture Decisions And Tradeoffs

Learn the craft of deciding in architecture: how to make decisions under uncertainty, make trade-offs explicit, record them in Architecture Decision Records (ADRs), and defend them with evidence instead of opinion. The core idea of this guide is that architecture isn't a diagram, it's a set of decisions — each with a cost, a reversibility, and consequences — and that "there's no best, only trade-offs" between quality attributes. You build a decision matrix with weighted criteria and sensitivity analysis, write ADRs in Nygard format (Context/Decision/Consequences/Status), generate and test alternatives with spikes before committing, and protect each decision with a fitness function that fails automatically if the system crosses a threshold. You also work through the cost and reversibility of deciding: one-way vs two-way doors, the last responsible moment, and technical debt as a deliberate trade-off. Everything quantifiable is executed in Python, not eyeballed. You work on Mercado's open decisions — should orders and shipping communicate synchronously or through events? should the catalog be extracted into its own service? — and close with a project where you make and record a real architectural decision end to end.